BUX85 NPN Bipolar Transistor Equivalent & Substitute Parts

Part Overview

The BUX85 is an NPN bipolar junction transistor manufactured by onsemi, rated for 450 V collector-emitter breakdown voltage and 2 A maximum collector current in a TO-220-3 through-hole package. This device is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements. The BUX85 delivers 50 W maximum power dissipation with a 4 MHz transition frequency, suitable for general-purpose switching and amplification applications in industrial and consumer electronics.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	450	V
Current - Collector (Ic) (Max)	2	A
Power - Max	50	W
Frequency - Transition	4	MHz
DC Current Gain (hFE) (Min) @ Ic, Vce	30 @ 100mA, 5V	—
Vce Saturation (Max) @ Ib, Ic	1V @ 200mA, 1A	—
Operating Temperature Range	-65 to 150	°C
Package / Case	TO-220-3	—
Mounting Type	Through Hole	—

Substitute Part Grouping Explanation

Substitute parts for the BUX85 are classified into two categories based on electrical and mechanical parameter alignment:

Direct Equivalent (Pin-Compatible, Identical Electrical Ratings): The BUX85G from onsemi maintains identical electrical specifications including 450 V breakdown voltage, 2 A maximum collector current, 50 W power dissipation, and 4 MHz transition frequency. Both devices use the TO-220-3 package with through-hole mounting. The BUX85G is the active production variant of the BUX85 series and serves as the primary direct substitute.

Similar Substitute (Enhanced Ratings, Same Package): The TSC741CZ C0G from Taiwan Semiconductor Corporation operates within the same voltage class (450 V) and package type (TO-220-3) but offers enhanced current handling (2.5 A versus 2 A) and increased power dissipation (60 W versus 50 W). This device is suitable for applications requiring higher current capacity while maintaining voltage compatibility. The transition frequency specification is not provided for the TSC741CZ C0G, and the DC current gain is higher (50 @ 100mA, 5V versus 30 @ 100mA, 5V).

Substitution eligibility is determined by matching the following critical parameters: transistor type (NPN), collector-emitter breakdown voltage (450 V), package type (TO-220-3), and mounting method (through-hole).

Parameter Comparison

Parameter	BUX85	BUX85G	TSC741CZ C0G
Manufacturer	onsemi	onsemi	Taiwan Semiconductor Corporation
Transistor Type	NPN	NPN	NPN
Voltage - Collector Emitter Breakdown (Max)	450 V	450 V	450 V
Current - Collector (Ic) (Max)	2 A	2 A	2.5 A
Power - Max	50 W	50 W	60 W
Frequency - Transition	4 MHz	4 MHz	Not specified
DC Current Gain (hFE) (Min) @ Ic, Vce	30 @ 100mA, 5V	30 @ 100mA, 5V	50 @ 100mA, 5V
Vce Saturation (Max) @ Ib, Ic	1V @ 200mA, 1A	1V @ 200mA, 1A	2V @ 600mA, 2A
Current - Collector Cutoff (Max)	200 µA	200 µA	250 µA
Operating Temperature Range	-65 to 150 °C	-65 to 150 °C	Up to 150 °C
Package / Case	TO-220-3	TO-220-3	TO-220-3
Mounting Type	Through Hole	Through Hole	Through Hole
Product Status	Obsolete	Active	Active
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

BUX85G (Direct Equivalent): The BUX85G is the recommended primary substitute for the obsolete BUX85. This device is manufactured by the same supplier (onsemi) and maintains identical electrical specifications across all critical parameters. The BUX85G holds active product status and is ROHS3 compliant, making it suitable for new designs and production environments with modern regulatory requirements. Inventory availability is significantly higher (19,830 pieces) compared to the original BUX85 (1,840 pieces), ensuring supply chain continuity.

TSC741CZ C0G (Enhanced Substitute): The TSC741CZ C0G from Taiwan Semiconductor Corporation is suitable for applications where higher current capacity (2.5 A versus 2 A) and increased power dissipation (60 W versus 50 W) provide design margin. This device maintains the same 450 V breakdown voltage and TO-220-3 package compatibility. The TSC741CZ C0G is ROHS3 compliant and holds active product status. Selection of this device is appropriate when circuit design permits the use of higher-rated components or when enhanced thermal performance is beneficial. The higher DC current gain (50 versus 30) and increased saturation voltage (2V @ 600mA, 2A versus 1V @ 200mA, 1A) must be evaluated against specific application requirements.

Both substitute parts are REACH unaffected and carry the same ECCN and HTSUS classifications as the original BUX85.

Frequently Asked Questions (FAQ)

Q: Can the BUX85G be used as a direct replacement for the BUX85 without circuit modification?

A: Yes. The BUX85G maintains identical electrical specifications including voltage rating (450 V), current rating (2 A), power dissipation (50 W), transition frequency (4 MHz), and DC current gain (30 @ 100mA, 5V). Both devices use the TO-220-3 package with identical pinout. No circuit modification is required.

Q: What are the key differences between the BUX85G and TSC741CZ C0G?

A: The primary differences are collector current rating (2 A versus 2.5 A), power dissipation (50 W versus 60 W), DC current gain (30 versus 50 @ 100mA, 5V), and saturation voltage (1V @ 200mA, 1A versus 2V @ 600mA, 2A). The transition frequency is specified for the BUX85G (4 MHz) but not provided for the TSC741CZ C0G. Both devices share the same 450 V breakdown voltage and TO-220-3 package.

Q: Is the TSC741CZ C0G suitable for applications originally designed for the BUX85?

A: The TSC741CZ C0G is suitable when the application circuit design permits the use of higher-rated components. The enhanced current and power ratings provide additional design margin. However, the higher saturation voltage and different DC current gain characteristics must be verified against specific circuit requirements to ensure proper operation.

Q: What is the significance of the product status difference between BUX85 (Obsolete) and the substitute parts (Active)?

A: The obsolete status of the BUX85 indicates that onsemi has discontinued production and support for this device. The active status of BUX85G and TSC741CZ C0G confirms ongoing manufacturing, technical support, and supply availability. For new designs and production, active-status devices are required to ensure long-term component availability and compliance with current manufacturing standards.

Q: Are both substitute parts RoHS compliant?

A: Yes. Both the BUX85G and TSC741CZ C0G are ROHS3 compliant. The original BUX85 is RoHS non-compliant. For applications subject to RoHS regulations, either substitute part is acceptable.

Q: Do the substitute parts have the same package and mounting type as the BUX85?

A: Yes. Both BUX85G and TSC741CZ C0G use the TO-220-3 package with through-hole mounting, identical to the BUX85. PCB layout and thermal management considerations remain unchanged.

Q: What is the inventory status of these substitute parts?

A: The BUX85G has 19,830 pieces in stock, significantly higher than the original BUX85 (1,840 pieces). The TSC741CZ C0G has 1,128 pieces available. For long-term production requirements, the BUX85G offers superior supply chain security.

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